Heating, ventilation, and air conditioning systems (HVAC) are used in commercial and residential buildings to condition the air to a desired temperature. HVAC systems typically utilize an air handling unit which comprises a furnace for heating the air, an evaporator coil connected to an exterior condensing unit for cooling the air, and a transition duct for connecting the furnace to the evaporator. A blower fan draws air from a return vent in the structure and pushes the air past the furnace and evaporator coil. In a heating cycle, the air is heated as it passes over a heat exchanger in the furnace. In a cooling cycle, the air is chilled as it passes over the evaporator coil.
In a conventional gas furnace, the heat is generated by main burners which are fired to heat a sealed heat exchanger. The exhaust gases from the combustion process are then vented through flue pipe and out of the structure. As the air is blown over the heat exchanger, the air is heated and is then distributed in a duct system through the structure.
In a conventional air conditioning system, a condensing unit is located outside of the structure to condense the working fluid in the system. Heat generated during the compression of the fluid is released to the atmosphere, and the compressed fluid is then pumped to the evaporator coil. The compressed fluid cools as it expands and flows through the evaporator coil, and this change in enthalpy chills the air as it is blown over the exterior surface of the evaporator coil. As this occurs, humidity in the air condenses o the exterior surface of the evaporator coil and is collected by a drain pan which carries the condensation away from the evaporator coil. This condensation is typically drained to a waste plumbing line or to a point outside of the structure.
Conventional heating and cooling systems lose efficiency because excess heat from the furnace is vented to the ambient surroundings, and energy is expended in the condensation of water on an evaporator coil. A need, therefore exists for an air conditioning system which improves the efficiency of heating and cooling systems.